<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/163965>163965</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            feature: Optional version of Clang module map `requires` declaration
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          torarnv
      </td>
    </tr>
</table>

<pre>
    As described in https://discourse.llvm.org/t/module-map-requires-as-non-hard-requirement/88589 we're looking for a way to provide Clang module maps for Qt for use with Swift, in a way that guarantees these module maps are _not_ accidentally picked up when building C++/Objective-C code (to avoid #158249 and other possible issues).

I initially thought `requires` would solve this, where Clang would ignore the module if the compilation unit doesn't match the required environment, but I now understand it's a hard error.

It would be nice if there was a syntax to declare a module map as having non-fatal requirements, that effectively hides the module (or submodule) if those are not met.

Thanks! 🙂
</pre>
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